Grinding plate glass



Dec. 17, 1929. J. P. CROWLEY GRINDING PLATE GLASS Filed April 10, 1924Patented @en il?, i929 entran `s'ra'rlzs PATENT y OFFICE/ .mamen '.e.cnowtnr,

OF TOLEDO, OHIO, ASSIGNR TO LIBBEY-OWENS GLASS COMPANY, OF TOLEDO, OHIO,A .CORPORATION OF( OHIO enr'nnrnernmn Grass .appncauoafupd april 10,

rllhis invention relates to the art of grind-A ing plate glass, and moreparticularly-to a 4new and improved abrasive mixture and acontinuousprocess for grading the same.

, Accoid11g .,t0.this invention a mixture `of substantially puresilica-sand and Crystalline garnet, suspended in Water, is first passedthrough a grading apparatus of the flotation type vvherein the materialssettle out in a in series of distinct grades which are drained ed intosuitable storage receptacles.v These diHerent grades of abrasive aremaintained in suspension in the storage receptacles and a continuouscirculation system which carries the abrasive ypast the several grindingma;l` 'chines, and portions of the several grades,

successively from coarse to fine, are drawn from these circulatingsystems and fed to the contacting surfaces of the glass sheet and 2e thegrindingtool. rllhe used material is col lected-'and 'pumped back to thegrading sys: tem Where it is regraded and returned to the circulatingsystem. The harder and heavier garnet, which does the greater part ofthe cutting in the first coarse grinding process, Will be deposited inthe heavier grade of abra-4 sive, Whereas the softer and finer sand willpredominate in the finer grade used for the smoothing process. ln thisWay the entire grinding. operation is carried out rapidly andefficiently and a very smooth finish obtained'on the glass plate. lf the'abrasive vmaterials are first mixed in the proper proportions and fedto the 'grading apparatus, the continuous grading process will becarried out automatically and the respective material distributed to thebest advantage inl the several grades of abrasive mixture.

rihe invention will hemore clearly understood from the'folloavingdetailed description of one typical system for grading and supplyingthis improved abrasive mixture. to a-series of-grinding machines. y yTheaccompanying drawing sli'ovvs diagrammatically a grading and abrasivefeeding system adapted to continuously supply the abrasive mixture to aplurality of grind- -ing machines;

At 1 is shown a grader of the flotation type comprising a series ofseparate compartments The unused ab pipe line 25.

1924. seri-a1 Np. 705,449.

2 to 7 respectively, the abrasive materials mixed with Water being fedinto the first compartment 2' through a feed pipe 8. A screen 9below'the pipe 8'serves to remove any excessively large-grainedmaterials that may I vhave found their Way into the mixture. The

mixture in receptacle 2 flows over the partition 10 into the receptacle3 wherein the glass level is slightly lower than in the rst receptacle2. In the same manner the mixture .in

compartment 3 iiows over partition 11 into compartment 4 and so `onthroughout the series. The larger grained and heavier materials willsettle out in the first tank 2, the next heaviest materials Will settleout in compartment S and so on, the finest material suitable for usesettling in the last compartment 7. The excess Water and suspendedmaterials too fine for abrading purposes will pass out through theoverovv pipe 12. It is to be understood that although six compartmentsare here shown, this nu-mber is merely illustrative and that any-desirednumber might be used. In the present mechanism three grades of abrasiveare used in the grinding process.

The materials deposited in the rst two receptacles, numbered 2 and 3respectively, are drained off through pipes 13 and 14 into a storagereservoir 15. In the same Way the material from tanks 4 and 5 iscollected in a vreservoir 16 and the finest material `from tanks 6 and 7is collected in reservoir 17. Sufficient Water is added in eachreservoir to bring the mixture to the proper consistency, and aconstantly driven agitator 18 is provided to keep the material in thereservoir in suspension. I

By means of a suitable pump 19 the heaviest grade of abrasive in tank orreservoir 15 is forced through a pipe line 20 Whichextends past each ofa series of grinding machines 21. rasive in pipe 20 flows back and isdischarged into the top of tank 15 as at 22. ln an exactly similarmanner the medium grade of abrasive in tank 16 is forced through pipeline 23 the unused abrasive being discharged back into tank 16 at 24. Inthe same manner a supply of the finest grade of abrasive from reservoir17 is maintained in the VA supply pipe 26 has valvedconnections Iat itsupper end With each of the circulation pipes 20, 23- and 25, and atA itslower end isa'dapted to dischargetheabrasive. mixture from a spout 27onto the upper face of the.

' glasssheet28 beneath'the grinding tool 29. The unusedlabrasivethroivnoif from'the rotatin'g sheet and 'grinding tool, as Well astheused abrasive 'Which has been vreduced insize by the grinding process,is collected in the housing 30 and drained through pipe 31 into a sump32. From this sump'the abrasivemixture. is lifted vby' pump .throughpipev '34; and discharged 'into the grading tank 2 at 35 along withthenew abrasive that may be addcd through feed pipe 8. Thisused abrasivethen passes .through the series of grading tanks, and is properlydistributed to theseveral reservoirs `15, 16 and 17 .The grading andfeeding system briefly def scribed above is disclosed. more in detailand claimedin'm'y 'copending application, Serial 4No. 682,495,1iledDecember 24 1923z According 4to'` the present linvention a mi'Xf ture ofsilicasand, and crystalline garnet', linapproximately the proportionsof' ten .parts sand to one part garnet, are mixed with Water 1 and fedthrough pipe'S-to the grading mechaf nism.- Thel garnet should be of a.grade that will pas'sthrough a 150 mesh screen. The

-v principal function ofthe garnet'is to perlform vthe rough grindingoperation. The sand shouldl be no heavier .than Will-pass throughal()mesh screen, and a large pro-` portion ofit will be much finer thanthis'. The sand-used is substantially pure 'silica-` 'sand, which has ahardness sulicientto per- I yform the iin'al smoothing process fvvithoutthe aid of any harder abrasives such as emery or garnet. This sandperforms the double func?v tion of operating asa cushioning medium forthe garnetdurmg the rough and intermediate grinding operations, andServes as the amount of the fine sand Will be carried down in theselirst tanks by the heavier garnet crysprocess.: f 1 Since cificgrav1ty,'a large proportion 'of the garnet main abrasive agentinthefinal smoothing ,Willsettle out in the first grading tanks, and avery small proportion, and thatof the finest grade, Will pass throughthe series to-find Yits Way into the mixture usedlfor smoothing pur--poses. The heavy sand will Isettle out infthe first tanks, and at thesame time' a large tals. In-this Way the abrasivemixture in 'tank 15,used for the v rough grinding process,

I Awill 'contain most Aof the garnet, all of the heavy sand and a largeproportion of lighter' sand. The medium grade of abrasive `in tank 16Awill cons/ist of the intermediate grades of sand, Withgasmallpercentage of the finer garnet. The finestabrasive, 'in tank 17,`u sedfor the final smoothing process, Will be nearly all sand vofexceedingly'fine grains, l

the garnet has a relatively high spe- The garnet crystals are harder andsharper- 'than the sand 'and-morefefficientffor cutting away ythe glassin th'eflirs't rough4 grinding process.. At. the Sametime the' sand inthe mixture vWill actas a cushioning agent between" the grinding tooland the glass to pref vent the garnet crystals froni`-grooving ytheglasstoo deeply." This cushioning Aaction of'. the sand Will be especiallyeffective' in the' intermediate and inal grinding' processes Where it isquite importa-nt' to prevent the scoringof the sheet-Which would 'takeplace if the harder garnet crystals were usedalone. l

In systems'where garnet orfother hard abrasives areused for'the finalsmoothing process,

' from iinding veir Way into the smoothing process to preit anylargegrainsof garnet .quantity of ythisabrasive to'- the apparatus, otherwisetheA surface of the glass Will become scratched or scored andv thesheetruined lin l -thepresent process the use oi a large (piantityv votvery. line silicasand v'for this smoothing abrasive willr quickly andeffectively perform the smoothing operation and at the same time protectthe Vglasstroml anyy garnet-particles.

,that Vmay findrthe'ir Way into this mixture, and serve as a cushionbetween the tool and the glass sheet to prevent the too rough grin'd-Ving action oftthis garnet. This smoothing sheet Without danger ofyinjuring thesame. y

less violent smoothing action of the sandare mixture may be freelyappliedto the glass It will beseenthat With this system the'` rapidgrinding action of the garnet, and the .distributed thmugh the differentStages' of the grinding process so as to obtain the mostl"effectiveresults The proper sorting of the materialtakes placeautomati-cally, and the' lcli-f 'fereut grades of material-'may be fedJfreelyto the apparatus Without any intermediate -ivashing processes,and the total grinding ieu `time Will'be much shorter than Would -be the'case ifieither material Were used separately or' if` the 'two materialswere fed separately smoothing the sheetwith fine silica-sand,

grinding plate glass, 'the iio abrasive actionof the garnet, andthenilmD grading the 4mixture by va settling'procesa Wherebythecoarse-rfgrad'sv contain most of the garnet, the grinding andsmoothingabra- "sives both being obtained from the same continuous gradingprocess.l

-., 2.l In the art of grinding plate glass, the' process of suspending amixture of silicasand and garnet in Water, grading the mixture by a'settling process, and successively.

fsa it is necessary to vuse a very accurate grading mageos feeding thegrades, :fromy coarse to ne, to a grinding mechanism. i

3. In the art of grinding plate glass,` the process of suspending amixture of silicasand and garnet in Water, grading the mixturebyasettling process whereby the greater.

portion of the garnet is contained in the' coarser. grades, successivelyfeeding the grades, from coarse to fine, to a grinding mechanism,collecting the used abrasive and returning it through the gradingprocess.

4. lin the art of grinding plate glass, the process of suspending amixture of silicasand and garnet in Water, grading the mixture by asettling process, whereby the coarser grades contain most of the garnet,and successively feeding the grades, from coarse to ine, to a grindingmechanism.

5.' in the art oi grinding plate glass, the process of suspending amixture of silicasand and garnet in water, grading the mixture by a.settling process whereby the greater portion of the garnet remains inthe coarser grades, again suspending each' grade of the mixture in Waterand maintaining it in suspension Vby agitation, successively feedingsome of each grade, from coarse to line, to

the grinding mechanism, collect-ing the used abrasive and returning itto the grading process.

Signed at Toledo, in the county of Lucas and State of Ohio, this 7th dayof April,

JOSEPH l". CRVVLEY.

